Road surface friction (RSF) influences the magnitude of tractive forces capable of being transmitted between a vehicle and the road. These tractive forces are commonly transmitted through a wheel and tire system. RSF is generally lower for a wet or ice-covered road surface than for a dry road surface.
Many accidents occur because a driver is not aware of RSF changes before he rounds a curve or applies braking in time to avoid an accident. This is particularly true at the beginning of a rain storm or as ambient temperature drops through the freezing point of water or salt water. The practice of salting highways makes it more difficult to determine the ambient temperature at which road surface icing occurs. Lightly applying brakes to determine how slippery a road surface is could cause loss of control of a vehicle if RSF conditions are poorer than expected. There is a need for this invention to alarm a driver of deteriorating RSF conditions before they become humanly perceptible.
The purpose of this invention is to inform the driver of a motor vehicle of changing road surface friction (RSF) conditions as they occur through an on-board alarm system so that vehicle operational adjustments, such as lowering speed or stopping, can be made before an accident occurs.
A system to measure the road surface friction of a road surface and to advise the driver of the condition is disclosed. The system has a means for measuring or sensing the RSF condition and a means for transmitting the RSF condition to the driver.
The system described above is most preferably mounted on the vehicle. There are two different methods disclosed for measuring or sensing, analyzing and transmitting the RSF condition to the driver. The first method disclosed is an on-vehicle RSF measurement system for measuring or sensing the RSF condition which is a part of the rotating vehicle wheel and braking system.
The second method disclosed is an on-vehicle RSF measurement system for measuring or sensing the RSF condition which is independent of the rotating vehicle wheel and braking system.
Data from either or both measurement systems is analyzed and used to alarm the driver of changing RSF conditions.